1. Field of the Invention
The present invention relates to a mobile, bi-planar x-ray imaging apparatus. More particularly, the present invention relates to a x-ray imaging apparatus having two imaging systems each disposed on two, independently movable C-arms with a control system in communication with both imaging systems such that they alternate taking x-rays.
2. Prior Art
It is often desirable to take X-rays of a patient from a number of different positions, preferably without the need for frequent repositioning of the patient. It is preferable that the X-ray support structure not unduly encumber the space immediately surrounding the patient to enable a physician to treat or otherwise attend to the patient without the need to repeatedly remove and replace the X-ray equipment. Mobile C-arm X-ray diagnostic equipment has been developed to meet these needs and has become well known in the medical art of surgical and other interventional procedures.
A C-arm refers generally to an elongate C-shaped member terminating in opposing distal ends of the "C" shape. An X-ray source and an image receptor are typically mounted at or near the distal ends, respectively, of the C-arm in opposing orientation, with the C-arm supported in a suspended position. The space within the C-shape of the arm provides room for the physician to attend to the patient substantially free of interference from the X-ray support structure. The support structure usually rests upon wheels which enable the C-arm to be wheeled from room to room, and along the length of a patient while the physician operates or examines, ensuring that devices such as cardiac catheters, long bone nails, etc. are properly positioned during the procedure.
The C-arm is usually mounted so as to enable rotational movement of the arm in two degrees of freedom, i.e. about two perpendicular axes in a spherical motion. More specifically, the C-arm is slidably mounted to the support structure to enable orbiting rotational movement of the C-arm about its center of curvature, thereby permitting the X-ray source and the image receptor to be selectively oriented vertically, horizontally, or somewhere in between. The C-arm is also laterally rotatable, i.e. in a perpendicular direction relative to the orbiting direction to enable selectively adjustable positioning of the X-ray source and receptor relative to both the width and length of the patient. The spherically rotational aspects of C-arm apparatus allow the physician to take X-rays of the patient at an optimal angle as determined with respect to the particular anatomical condition being imaged.
Designers and manufacturers of C-arm equipment are faced with a number of challenges. The support structure used to support and rotate a C-arm in its various suspended positions must be strong enough to withstand tremendous torsional, tensile and compressive stresses. The support structure must also be heavy enough and have a large enough footprint to avoid tipping over upon lateral rotation of the C-arm, which causes the center of gravity to shift dramatically. There have been previous attempts to provide C-arm support structure to solve the problems mentioned above. Exemplary of such prior art attempts is U.S. Pat. No. 4,955,046 (issued to Siczek et al. on Sep. 4, 1990) which discloses a C-arm apparatus. A wheeled support cart includes a rotatable L-arm upon which a C-arm is slidably mounted. The L-arm thus provides rotational movement of the C-arm in two degrees of freedom.
In addition, it is often desirable to take X-rays of a patient from a number of different angles, preferably in quick succession and without repositioning the C-arm. Such a configuration is often referred to as bi-planar imaging and allows an object to be viewed in two planes simultaneously. The two X-ray beams emitted from the two X-ray tubes may cross at an iso-center. Bi-planar imaging is useful for checking a catheter position, a balloon status or performing a digital subtraction run.
Bi-planar imaging may be accomplished in several ways. One way is by using two independent imaging systems, or two C-arms. U.S. Pat. No. 4,884,293 issued Nov. 28, 1989, to Koyama discloses a dual imaging system with one imaging system being mounted to the floor and the other being mounted to the ceiling. One disadvantage of this system is that it is permanently mounted to the floor and ceiling. Thus, the system cannot be moved about a hospital as needed. Another disadvantage of this system is that, although the C-arms are coordinated, the imaging systems operate independently of one another. Thus, the images produced are not coordinated.
Another configuration for obtaining bi-planar imaging is slidingly nesting one C-arm in another. U.S. Pat. No. 5,515,416 issued May 7, 1996, to Siczek et al. discloses a dual imaging system with one C-arm being mounted to the floor and the other C-arm being slidingly disposed on the first C-arm. One disadvantage of this system is that the two imaging systems may not be moved independently of one another. Thus, the positioning of the second imaging system is limited by the position of the first. Another disadvantage is that it is permanently mounted to the floor. Thus, it cannot be moved about a hospital. A further disadvantage is that the two images must share a common iso-center because they are nested.
Another configuration for obtaining bi-planar imaging is disposing the imaging systems in a ring, as opposed to C-arms. U.S. Pat. No. 3,549,885 issued Dec. 22, 1970, to Andersson discloses a dual imaging system with both imaging systems being mounted perpendicularly in a rotatable ring. One disadvantage with this system is that the bi-planar images are always disposed at a fixed, perpendicular angle with respect to each other.
Another configuration for obtaining bi-planar imaging is disposing the imaging systems on a G-arm, as opposed to C-arms. U.S. Pat. No. 5,095,501 issued Mar. 10, 1992, to Kobayashi discloses a dual imaging system with both imaging systems being mounted perpendicularly in a G-shaped arm. Like the ring configuration above, one disadvantage of this system is that the bi-planar images are always disposed at a fixed, perpendicular angle with respect to each other.
Furthermore, it is often desirable to view X-rays in real time and to save or store X-rays taken of a patient for later review. It is difficult to operate both imaging systems at the same time because both systems typically operate independently. In addition, if both systems operate at the same time, the two X-ray beams cause a blurred picture and expose the subject to excessive radiation due to scattering.
Therefore, it would be advantageous to develop a mobile, bi-planar imaging system with independently movably imaging systems capable of being moved and capable of various bi-planar angles. It would also be advantageous to develop a bi-planar imaging system with a control system to automatically operate the imaging systems by alternately operating each imaging system. It would also be advantageous to develop a bi-planar imaging system capable of real time display and real time storage of images.